Electronic animal confinement system

ABSTRACT

A system (10) for confining an animal (18) in an area (16) defined by a boundary signal. The system includes a transmitter (22; 22A) to generate the boundary signal and an emitter such as a wire (20) to define area (16). The system also includes a receiver (26; 26A; 200; 200A) to be carried on the animal&#39;s neck. The receiver includes three selectively monitored and orthogonally-positional antennas (30, 32, 34; 202, 204, 206) to avoid missing a boundary signal. The receiver further includes code-detecting, duration monitoring and/or signal-strength circuitry (270) to control giving a shock to the animal. Further, the receiver is duty-cycled to conserve battery power (56). The shock is communicated via a conductive compliant tip (532) to reduce discomfort to the animal. The transmitter includes circuitry (64) to include a code in the boundary signal, and an isolation transformer (102) to protect the transmitter from energy strikes, such as lightning, at the emitter (20).

This application is a continuation of application Ser. No. 08/553,724,filed Oct. 23, 1995, now U.S. Pat. No. 5,682,839 which is a continuationof Ser. No. 08/092,084, filed Jul. 15, 1993, now issued as U.S. Pat. No.5,460,124, both of which are expressly incorporated herein by referencein their entirety.

APPENDIX

Attached hereto as Appendix A is an object code listing of software foruse with the FIG. 6 embodiment of a receiver for the present invention.The contents of Appendix A is incorporated herein by reference. Further,Appendix A contains material which is subject to copyright protection.The owner has no objection to facsimile or microfiche reproduction ofthe appendix as it appears in the Patent and Trademark Office patentfile or records, but otherwise reserves all rights whatsoever.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates to electronic animal confinement systemsand, more specifically, to such systems in which a receiver on theanimal responds to an electronic signal to alert the animal to staybehind a boundary that is electronically defined by the signal.

II. Description of Prior Art

Electronic animal confinement systems have become very popular becausethey use electronic signals to create a boundary rather than anunsightly fence. For example, a boundary signal emitter wire is buriedaround the perimeter of the yard in which a pet, such as a dog, is to beconfined. A transmitter hidden in the house or garage is electricallyconnected directly to the emitter to energize the wire with an RFboundary signal generated in the transmitter. The wire radiates the RFsignal to thus electronically define an imaginary "boundary" coincidentwith the wire. A receiver worn about the neck of the dog and responsiveto the radiated RF signal will sense or respond to the boundary signalas the dog approaches the boundary (e.g., the wire). The receiverincludes circuitry designed to provide a shock to the dog to cause thedog to move away from the boundary. As a result, the dog may be kept inthe yard without an unsightly fence.

Unfortunately, such systems are not without drawbacks. For example, insome situations, the receiver might not actually pick up the boundarysignal as the pet approaches the boundary allowing the dog to simply"run through" the boundary. Similarly, if the dog is trapped near theboundary, repeated shocks will be administered for as long as thebattery has power. Such long-term exposure to shocks is painful anddeleterious to the animal. In other situations, non-boundary RF signals,such as from AC motors, electric utility cables, television sets, or thelike, could be picked up by the receiver causing the dog to receive anunexpected and undesired shock even though the pet may not be near theboundary. Other problems have been experienced which further limit theutility of such animal confinement systems.

In a storm, for example, the wire acts not only as an emitter of the RFboundary signal, but may also attract energy such as from lightning.Should lightning strike at or near the wire, the transmitter circuitrymay be damaged or destroyed. Also, the receiver units worn by the petare battery-powered. It is not uncommon for the receiver to drain thebattery fairly quickly. As a result, there is the risk of failure of thesystem to keep the pet confined due to battery failure, as well as theannoyance of frequent battery replacement to avoid such failure. Anadditional problem with typical receivers is that the metal lugsextending from the receiver and into the pet's neck to shock the dog arevery hard and may tend to scratch or irritate the dog's neck.

SUMMARY OF THE INVENTION

The present invention provides an electronic animal confinement system,and receiver and transmitter components therefor, which overcome theabove-described drawbacks of prior art systems. To this end, and inaccordance with one aspect of the present invention, the receiver wornby the pet includes three orthogonally positioned antennas to insurethat whenever the animal is near the boundary, the boundary signal willbe detected. The circuitry within the receiver examines each one of theantennas, preferably one at a time, until the boundary signal isdetected. In response to detection of the signal on any one of theantennas, the circuitry provides an annoyance signal (such as an alarmsound or a shock) to the animal to prompt the animal to back away fromthe boundary. In this manner, the boundary signal should not goundetected as the pet approaches the boundary, thus minimizing thelikelihood that the animal might "run through" the boundary.

In accordance with another aspect of the present invention, the risk ofinadvertent shocks from non-boundary RF signals is greatly reduced. Tothis end, the electronic boundary signal from the transmitter is encodedwith a preselected signal such as by AM modulating an RF signal (e.g.,10 to 11 KHz) boundary signal with a code such as a low frequency (e.g.,10 to 1000 Hz) signal. The receiver circuitry includes a detectorcircuit that is responsive to the demodulated code signal and, only whenthat signal is found in the RF signal, is the annoyance signal provided.As a consequence, errant shocks from receipt of RF signals other thanthe boundary signal are minimized or eliminated.

Another feature of the present invention provides circuitry to avoidprolonged and possibly deleterious shocks to the animal. Should theanimal be trapped, for example, close to the boundary, the typicalreceiver continues to shock the animal, possibly until the battery isdrained. To avoid such a situation, in accordance with this aspect ofthe invention, if a shock is administered for more than a specifiedtime, such as twenty seconds, for example, a monitor mode is commenced.In the monitor mode, shocks are suspended but the circuitry continues tomonitor for the boundary signal. After the boundary signal hasterminated for a period of time, indicating that the animal has beenremoved from the boundary, the monitor mode is terminated. Thereafter,subsequent detection of the boundary signal will result inadministration of the annoyance signal once again. In this manner,prolonged and excessive administration of shocks is minimized oreliminated.

In accordance with a yet further aspect of the present invention, thebattery life of the receiver is extended to reduce the annoyance offrequent battery changes or too-quickly drained receiver batteries. Tothis end, at least some of the power draining circuitry is duty-cycledon and off so as to reduce power usage and extend battery life. Morespecifically, the RP front end of the circuitry which actually detectsand demodulates the received boundary signal need not necessarily be onat all times. Instead, that power-consuming circuitry is turned on for abrief interval and, if either no signal is detected or the receivedsignal is below some minimum threshold, the RF front end will be turnedoff again to conserve battery power. The above-mentioned monitor modefurther minimizes battery depletion as well. Still further, and toreduce the risk of a non-functional receiver due to a dead battery,circuitry is provided to monitor the battery and provide an alert whenthe battery is nearing the end of its useful life. The alert may be inthe form of a flashing LED on the receiver housing and visible to theuser to thus visibly warn the user to replace the battery well before itactually goes dead.

Microprocessor circuitry may be utilized to analyze the received signalsand to control institution of the annoyance signals. In that case, themicroprocessor circuitry may also be powered down when not in use andthen turned back on when a signal is received to be analyzed to furtherconserve power. Alternatively, or additionally, the circuitry mayinclude one or more motion sensors which allow the power-drainingcircuitry to be energized in response to movement of the animal suchthat when the animal is at rest and, therefore, not trying to cross theboundary, the battery is not wasted trying to detect a boundary signalthat should not be present.

To further enhance the utility of an electronic animal confinementsystem, two levels of annoyance signal may be employed. As the boundarysignal is first detected above the minimum threshold but below somehigher threshold (indicating that the animal is nearing but not yetadjacent to the boundary) an audible tone may be given. A trained animalwill often respond to the audible signal alone and retreat from theboundary thereby reducing the level of signal received by the antennaand obviating the need to shock the animal. If at any time the signalexceeds the higher threshold (as may occur if the animal is runningtowards the boundary, for example), the shock will be given right awayand may be given along with the audible warning. On the other hand,where the signal level remains below that higher threshold, but is stillabove the minimum threshold, it may be assumed that the animal has notwithdrawn. In such a case, the pet is to be administered a shock. Tothis end, the signal level is tested at brief intervals after theinitial audible tone warning is given. If the signal is still presentabove the minimum threshold for some period of time, a shock will beadministered whereas if either no signal is detected, or the signal isbelow the minimum threshold, the receiver will terminate the annoyancesignal sequence (tone-to-shock) until a subsequent signal above theminimum threshold is received at which time the sequence will beginanew.

In situations where continued presence of the signal is the basis for ashock, the period of time between the sounding of the tone andadministration of a shock may be selectively varied to accommodateanimals of different temperaments, mobility, behavior, etc. Whereseveral animals are within the same boundary, and thus have similarlytuned receivers, the delay(s) may be individualized to the specificanimal by selecting different delays in the respective receivers.

In accordance with a yet further feature of the present invention, themetal shock lugs of conventional receivers are replaced with flexible orcompliant conductive tips. These tips are more comfortable and thusreduce irritation to the pet, but still provide effective transfer ofthe shock to the pet when necessary.

With respect to the transmitter, the present invention provideslightning strike protection. To this end, and in accordance with a stillfurther feature of the present invention, the transmitter circuit outputis electrically isolated from the signal emitter (e.g., the buriedwire). The isolation may be provided by an isolation transformer, forexample, to thus allow the RF boundary signal to be coupled to the wirebut to isolate, and protect, the transmitter circuitry from high energystrikes such as from lightning.

By virtue of the foregoing, there is thus provided an electronic animalconfinement system, and receiver and transmitter components therefor,which provide advantages in performance and utility over prior artsystems. These and other objects and advantages of the present inventionshall be made apparent from the accompanying drawings and descriptionthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description given below, serve to explain the principles ofthe invention.

FIG. 1 is a diagrammatic view of an electronic animal confinement systemin use for purposes of explaining the principles of the presentinvention;

FIG. 2 is a schematic diagram of one embodiment of a receiver inaccordance with the principles of the present invention for use in theanimal confinement system of FIG. 1;

FIG. 3 is a schematic diagram of a first embodiment of a transmitter anda second embodiment of a receiver in accordance with the principles ofthe present invention for use in the animal confinement system of FIG.1;

FIG. 4 is a schematic diagram of a second embodiment of a transmitterincluding lightning strike protection in accordance with the principlesof the present invention for use in the animal confinement system ofFIG. 1;

FIG. 5 is a schematic diagram of a microprocessor-based embodiment of areceiver in accordance with the principles of the present invention foruse in the animal confinement system of FIG. 1;

FIG. 6 is a schematic diagram of a second microprocessor-basedembodiment of a receiver in accordance with the principles of thepresent invention fuse in the animal confinement system of FIG. 1;

FIGS. 6A-C are schematic drawings of modifications to parts of thecircuit of FIG. 6;

FIG. 7 is a block diagram of the receiver of FIG. 6 modified for usewith vibration or motion sensors to further conserve battery power;

FIG. 8 is a cross-sectional, exploded view of the housing for thereceivers of FIGS. 2, 3, and 5-7 showing the use of less-irritatingconductive tips to communicate a shock to the pet; and

FIG. 9 is a cross-sectional view of the housing taken along line 9--9 ofFIG. 8.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to FIG. 1, there is shown a diagrammatic view of anelectronic animal confinement system 10 for purposes of explaining thepresent invention. As seen in FIG. 1, a structure such as a house 12includes a front yard 14 in which an area 16 is to be defined as thearea in which the animal, such as a pet dog 18, for example, may moveabout freely. To define area 16, a loop of wire represented by dashedline 20 is buried in the yard 14 to define the boundary of area 16beyond which dog 18 is not to pass. The ends of wire 20 are electricallyconnected to transmitter 22 placed, for example, inside garage 24attached to house 12. Transmitter 22 generates RF boundary signals whichare radiated by buried wire 20 for reception by receiver 26 supported ondog 18 such as by collar 28 or the like.

As pet 18 approaches the boundary defined by RF boundary signals emittedfrom wire 20 (such as in the direction of Arrow A), the circuitry inreceiver 26 begins to detect that RF signal. When the received signalreaches above some threshold limit, an annoyance signal such as anaudible signal or a shock is administered by receiver 26 to pet 18 tocause pet 18 to withdraw, such as in the direction of Arrow B away fromboundary 20.

As will be readily appreciated, pet 18 will not always approach boundary20 from the same direction. Indeed, dog 18 may be running or jumping ina variety of directions such that the orientation of receiver 26 to wire20 is not fixed but is instead quite variable. As a consequence, theremay be certain positions at which receiver 26 might not be properlyoriented for a single antenna in receiver 26 to receive the boundarysignal. To obviate such a problem, receiver 26 is provided with a trioof orthogonally positioned antennas as will now be described withreference to FIG. 2.

Turning now to FIG. 2, it will be seen that receiver 26 includes threeorthogonally positioned antennas 30, 32, 34 positioned in the X, Y and Zorientations, respectively, within plastic housing 27 of receiver 26. Asa consequence, as receiver 26 moves about with dog 18, at least one ofantennas 30, 32 or 34 will be angled relative wire 20 so as to receive asignal thereon as animal 18 approaches the boundary. Each of theantennas is coupled through a respective analog switch 36, 38, 40 whichare selectively energized one at a time by ring or counter circuit 42,which selectively enables one of three outputs in response to pulsesfrom clock or oscillator 44. Preferably, oscillator 44 outputs a 30 Hzsignal so that each switch, 36, 38, 40 is closed ten times per second,it being understood that when any one of the switches is closed, theother two are open. Thus, only one of antennas 30, 32 and 34 at a timeis coupled through its respective switch to amplifier 50, whichamplifies any signal received on the selected antenna to a useful level.

The output of amplifier 50 is coupled to a peak detector 51 comprised ofseries diode 52 and shunt capacitor 53 and then on to comparator 54 forcomparison against a reference signal having a level defined by thevalues of resistors R₁ and R₂. The level of the reference signal isselected to correspond to the level of signal which would be receivedwhen animal 18 is deemed to be sufficiently close to boundary 20 tojustify giving the shock, for example, to the animal. Accordingly, ifthe peak-detected output of amplifier 50 exceeds the value of thereference signal input to comparator 54, comparator 54's output willenergize shock circuit 55 (which may, for example, include amultivibrator or oscillator and a step-up transformer) to generate highvoltage shocks. As a result, receiver 26 provides a shock to the animalvia conductive tips or probes 58 extending out of housing 27 and towardsthe pet's neck to thus cause animal 18 to back away from boundary 20.

Receiver 26 may be powered by a standard nine volt transistor battery56, for example, and may include an on/off switch (not shown) asdesired. Alternatively, and depending upon the requirements of theelectrical circuitry employed, battery 56 may be comprised of one ormore cells having a combined series voltage of 5.9 to 8.0 volts. It willbe appreciated that presence of battery 56 and any transformer (notshown) in shock circuit 55 may require that one or more of antennas 30,32, 34 actually be offset from its orthogonal axis to compensatetherefor. Hence, it is to be understood that reference to the antennasas being orthogonally positioned is meant to allow for any such offset.

In the receiver embodiment of FIG. 2, any RF boundary signal ofsufficient signal strength in the pass band of the antennas andamplifier 50 will cause a shock to be administered to pet 18. Thus,shocks may be given in response to non-boundary RF signals. Inaccordance with a further aspect of the present invention, such spuriousand undesired shocks may be reduced or eliminated by provision of acoded boundary signal. To this end, and as seen in FIG. 3, transmitter22 may include an RF boundary signal oscillator 60 (e.g., operating at10 KHz), the output of which is coupled through an analog switch 62.Switch 62 is turned on and off in response to the output of lowfrequency (e.g. 30 or 90 Hz square wave) oscillator 64, such as to openand close switch 62 at the low frequency rate to thereby amplitudemodulate the output of oscillator 60. The result is a 10 KHz RF boundarysignal modulated with a 90 Hz square wave code, for example, asrepresented at 66. The modulated boundary signal is then coupled to wire20 for reception by receiver 26. Although a simple low frequency squarewave code is shown, it will be readily appreciated that other, morecomplex codes could be employed.

Receiver 26A, as also shown in FIG. 3, is like receiver 26 of FIG. 2,but further includes a demodulator such as a phase locked loop 70 and acode detect circuit 71, which is responsive to receipt by one ofantennas 30, 32 or 34 of the RF boundary signal that includes thereonthe code (such as the 90 Hz amplitude modulated signal) from transmitter22. In that circumstance, where the RF boundary signal satisfies thecriterion of having a valid code therein, the output of detect circuit71 will enable an audible annoyance alert from an audible sounder suchas a speaker or resonator 72. Until a valid code is detected, the outputof detect circuit 71 is a logic low which clears delay counter 73 sothat its outputs are all low. Upon detecting a valid code, the output ofcircuit 71 goes high to not only sound the alert but to also enablecounter 73 to begin counting out the delay period. If the detectedsignal remains for a selected duration, i.e., it does not terminatebefore counter 73 times out (the selected Q output goes high), a signalwill be output therefrom through OR gate 74 to enable shock circuit 55to administer a shock to animal 18. Additionally, and irrespective ofthe delay of counter 73, if a signal is detected that indicates pet 18is sufficiently close to boundary 20 to warrant a shock in any event,the output of comparator 54 will go high. In that event, and if a validdetect signal is indicated by circuit 71, AND gate 75 will output alogic high signal to directly enable shock circuit 55 through OR gate 74without delay. Thus, when the received boundary signal satisfies a firstcriterion (e.g., the code), and also satisfies a second criterion (e.g.,either duration or signal strength), a shock will be administered. Ineither case, because a valid code must be detected in the boundarysignal, only when animal 18 approaches the boundary defined by signalsemitted from wire 20 will a shock be administered rather than inresponse to an errant RF signal such as from an AC motor or other RFsignal emitter which may be in the area.

To allow use of receiver 26 with variable tone-to-shock delays setuniquely for each animal 18 equipped with such a receiver, a selectormay be provided. To this end, switch 76 has at least a first state and asecond state to selectively connect the lower order Q_(A) output or thehigher order Q_(B) output of counter 73 to OR gate 74 by which to varythe delay period, or duration, as desired by the user (not shown). Otherintermediate delays may be selected by utilizing other intermediateorder outputs (not shown) of counter 73 as will be readily appreciatedby those skilled in the art.

With reference to FIG. 4, there is shown a version 22A of transmitteradapted to provide coded boundary signals similar to that shown forreceiver 22 in FIG. 3, but also including lightning strike protection aswill be described. Transmitter 22A of FIG. 4 includes a power supplysystem 80 which is provided with AC power from plug 82 plugged into awall outlet (not shown) such as in garage 24. Power from plug 82 iscoupled to the primary of power transformer 84 via fuse 86. Theparallel-connected dual secondaries of transformer 84 are connectedthrough on/off switch 88, which is operable in conjunction with wiper 89of potentiometer 90, to full wave-rectifier bridge 92. Bridge 92 iscoupled to 330 μF/50 volt capacitor 94 to provide unregulated 18 voltsDC at 96. The unregulated DC at 96 is coupled to a high efficiencyswitch mode adjustable power supply 98 (such as constructed with anMC34063 device and having a choke and thermistor in the output andcompensation circuit lines) to provide 2-16 volts on output 100 to driveisolation transformer 102 as will be described. The output level fromsupply 98 is adjusted by varying wiper 89 of 10 kilohm potentiometer 90to thereby adjust the strength of the RF boundary signal radiated bywire 20. By thus varying signal strength, it is possible to adjust theminimum allowable distance between wire 20 and pet 18 at which anannoyance signal is to be administered. Adjusting wiper 89 so that thevoltage on output 100 decreases past its minimum will also cause switch88 to open thereby turning transmitter 22A off. Thus, to turntransmitter 22A on, wiper 89 of potentiometer 90 is rotated to closeswitch 88 and begin increasing the power level output from supply 98 foruse with isolation transformer 102.

The DC level at 96 is also coupled to a low voltage power supply 104(such as a 7805 voltage regulator) to provide on its output regulated 5volts DC to power oscillators 60 and 64. The output of oscillator 64 iscoupled to the enable input 106 of oscillator 60 to thereby turnoscillator 60 on and off at a 50% duty cycle 90 Hz rate to produce onoutput 108 the 10 KHz modulated with 90 Hz square wave coded boundarysignal as previously described (as at 66). That signal is coupled to thegate input of N-channel Mosfet 110 (type IRFZ30) which is coupled inseries between isolation transformer 102 and ground to thus cause thecoded boundary signal to be coupled into primary winding 111 ofisolation transformer 102. The secondary winding 112 of transformer 102is center-tapped to ground to provide a bi-polar output. At one end 113,transformer secondary winding 112 is coupled through 1 ohm/1 wattcurrent limiting resistor 114 to terminal 116 which is coupled to oneend of wire 20. The other end of wire 20 is coupled to terminal 118.Terminal 118 is coupled through three series diodes 120 (type 1N4003) tothe other end 122 of secondary winding 112 of transformer 102. Ends 113and 122 are also coupled through 33 volt metal oxide varistor transientsuppressors ("MOV") 124 to the center-tapped ground. Connected inparallel across terminals 116 and 118 is a 68 volt MOV 126. A centerterminal 128 may be provided for a ground connection between yard area16 and the system ground.

Transmitter 22A is further provided with a loop-open indicator comprisedof 18 ohm resistor 130 in series with the light emitting diode 132 ofoptoisolator 134 (type 4N26), all in parallel with the three diodes 120.Optoisolator 134 includes light sensitive NPN transistor 136 which turnson in response to light from diode 132 caused by current flowingtherethrough. Current flows through diode 132 when current flow throughwire 20 is degraded or interrupted such as when wire 20 is broken. Whentransistor 136 is thus closed, audio indicator 138 and light emittingdiode 140 are energized to thereby indicate that the loop created bywire 20 and, thus, the system may be nonfunctional.

It will be appreciated that by virtue of isolation transformer 102, thecoded boundary signal may be coupled to wire 20 while at the same timepreventing excessive power spikes from flowing back into transmitter 22Afrom wire 20. Thus, in the event of a significant energy stroke on ornear wire 20 such as due to lightning or the like, energy will bedissipated and not likely to be able to pass through isolationtransformer 102 into the circuitry of oscillators 60 and 64, or any partof power supply 80 at a level sufficient to damage or destroy thatcircuitry.

Although shown as discrete components, it will be readily appreciatedthat the function of oscillators 60, 64 and control of indicators 138,140 may be provided by an integrated circuit programmed device. One suchdevice is a PIC 16C54 microcontroller available from MicrochipTechnology Inc. in Phoenix, Ariz.

Turning now to FIG. 5, a microprocessor-based receiver 200 isillustrated. Receiver 200 is similar to receivers 26 and 26A butprovides part of the receiver circuitry as a programmed processor andincludes duty-cycling circuitry to conserve power. Receiver 200 includesthree orthogonally positioned 10 millihenry inductor antenna coils 202,204, 206, however, in this case they are connected in series so thatenergy received by any of them may be detected at all times. Coupled inparallel across the series antennas is 7500 pF capacitor 208. The outputof the antennas is coupled through 0.01 μF capacitor 210 and 22 Kohmresistor 212 to the inverting input of amplifier 214 which includes aparallel 330 Kohm resistor 216 and 22 pf capacitor 218 feedback networkto provide a low pass pole at about 15 KHz. Amplifier 214 is coupledthrough 22 Kohm resistor 220 to the inverting input of second amplifier222 which similarly includes a parallel resistor/capacitor feedbacknetwork to provide a low pass pole at about 15 KHz. The non-invertinginputs of amplifiers 214 and 222 are coupled through respective 22 Kohmresistors 224 to bias circuit 226. Bias circuit 226 includes anN-channel FET 230 (type MMBFJ309LT1) the channel of which is connectedbetween a selectively controlled source of power V_(A), and the seriescombination of 1 megohm resistor 232, 16 kilohm resistor 234 and 100kilohm resistor 236 to ground. Resistors 224 are coupled to groundthrough 0.01 μF capacitor 238 and to the junction of resistors 234 and236, via 10 Kohm resistor 240. The junction of resistors 232 and 234 iscoupled to the gate of transistor 230, to ground through 100 pFcapacitor 242 and to the inverting input of third amplifier 246, thenon-inverting input of which is coupled to the output of amplifier 222and to ground through 1 megohm resistor 248.

The output of amplifier 246 is coupled through 100 Kohm resistor 250 and1 megohm resistor 252 to the non-inverting input of fourth amplifier256. The junction of resistors 250 and 252 is coupled to ground through0.01 μF capacitor 258. The inverting input of amplifier 256 is biased toa preselected reference level by 2.2 megohm resistor 260 and 560 Kohmresistor 262 between a source of power V_(C) and ground. The output ofamplifier 256 drives an N-channel Mosfet 264 (type 2N7002), the channelof which is coupled between ground and, through 1 megohm resistor 266,to power supply V_(C). The junction of transistor 264 and resistor 266is a digital output that is normally at a high logic level (a "1") equalto approximately V_(C) and is driven low (a "0") to ground whenever asignal is received through RF front end amplifiers 214, 222, 246 and 256from antennas 202, 204 and 206 of sufficient strength to be indicativethat pet 18 is so near wire or other RF emitter source 20 such that animmediate shock may be needed to divert pet 18 away from the boundary.The output of transistor 264 is a "near-boundary" signal and is coupledover line 268 to one of the data lines (e.g., pin 18) of microprocessor270 (such as the aforementioned PIC 16C54 Microcontroller) forutilization by the microprocessor as will be described hereinafter.Processor 270 includes a 32.786 KHz crystal clock 272.

The output of third amplifier 246 is also coupled through resistor 250and 100 Kohm resistor 274 to the base of NPN transistor 276, the emitterof which is grounded and the collector of which is coupled through 1megohm resistor 278 to the positive terminal of battery 56 (designatedas V_(B)). The collector of transistor 276 (type MBT2222) is alsocoupled to the gate input of Mosfet transistor 280 (type 2N7002), thechannel of which is between ground and, via 1 megohm resistor 282,source of supply V_(C). The output from transistor 280 is normally logic"1" (at or near V_(C)). In response to RF energy at an appropriate levelfrom amplifiers 214, 222 and 246, the circuitry previously-describeddemodulates the RF or high frequency therefrom. The resultant signal isa low frequency signal, if any were modulated on the received RF signal,which is alternating between a logic low and a logic high on line 284corresponding to the low frequency modulation on any RF signal detectedby antennas 202, 204, 206. That low frequency signal, the "code-detect"signal, is coupled via line 284 into a data line (e.g., pin 1) ofmicrocontroller 270 for examination. That signal could also oralternatively be provided to the real time clock count pin (pin 3). Thesignal thus received is examined by processor 270 to determine if itcorresponds to the anticipated low frequency or "code" expected. If so,then microcontroller 270 will utilize that information to controlgeneration of an audible tone and/or shock to pet 18 as will bedescribed.

In order to conserve battery life, the active portion of the RF frontend (amplifiers 214, 222, 246 and 256) is intermittently energized. Tothis end, each of the amplifiers is selectively powered from a source ofsupply V_(A), which is provided by the output of multivibrator circuit290. The output is a 10% duty cycle pulse which is on for 30milliseconds and off for 300 milliseconds, for example, to thusinterrogate for energy from antennas 202, 204, and 206 approximately 3times per second. Circuit 290 is powered by V_(B), i.e. from battery 56,and thus is operating at all times that battery 56 has sufficientcharge. Duty cycle circuit 290 can also be forced to output a steady"on" voltage on its output V_(A) in response to flip-flop 292. Normally,the output of flip-flop 292 is at a logic level ("1") that allowscircuit 290 to operate in a free-wheeling mode to thus pulse the RFfront end on and off. In response to a signal on the S input offlip-flop 292, the output thereof will change logic states to a low("0") causing circuit 290 to force a logic high output on the V_(A)output to thus turn amplifiers 214, 222, 246 and 256 full on untilflip-flop 292 is reset by a signal on the R input thereof. Ordinarily,the S input of flip-flop 292 is tied to a logic high through 330 kilohmresistor 294 to V_(B), however in response to receipt of a signal ofsufficient strength at transistor 276, a negative going pulse is coupledthrough 0.001 μF capacitor 296 to cause the output of flip-flop 292 tochange states and thus control circuit 290 to turn the RF front end fullon. The R input of flip-flop 292 is also similarly tied to a logic highthrough 100 Kohm resistor 298 to V_(B), but when a low-going "reset"signal on a selected dataline from microcontroller 270 (e.g., from pin12) is output therefrom, it causes a negative going pulse to passthrough 0.01 μF capacitor 300, thereby resetting flip-flop 292 to onceagain allow circuit 290 to produce its periodic pulses.

Receiver 200 also includes a 3.1-volt regulator 310 such as aprogrammable low-dropout voltage regulator, type MAX667CSA, availablefrom Maxim Integrated Products in Santa Clara, Calif. Regulator 310 ispowered on its input terminal (pin 8) by V_(B). A "low battery" testinput is also provided (pin 3) which is coupled to the junction of 1megohm resistor 312 and 270 Kohm resistor 314 in series between V_(B)and ground. The shutdown input of regulator 310 (pin 5) is tied to V_(B)through 1 megohm resistor 316 to turn off (shut-down) regulator 310unless that input is pulled low. In this regard, the shutdown input isbe pulled to a logic low either through diode 318 (by the output offlip-flop 292 when it receives the negative-going pulse on its S inputindicative that a near-boundary signal may have been detected such thatprocessor 270 should stay powered up) or through diode 320 by a lowstate signal from pin 17 of processor 270 (referred to hereinafter asthe "keep alive" signal) which is utilized to maintain power toprocessor 270 in either low power standby or monitor modes as will bedescribed. Diodes 318 and 320 may be a dual diode package (typeMBAW56L). The DD input (pin 1) of regulator 310 is coupled to groundthrough 1 megohm resistor 322 and 330 Kohm resistor 324, and the setinput (pin 6) is coupled to ground directly through resistor 324 andcoupled to the 3-volt DC output (pin 2) through 1 megohm resistor 326.That output is V_(C). The low battery output line (pin 7) is pulled to alogic level high of V_(C) through 1 megohm resistor 327, and coupled toone of the datalines (pin 2) of microcontroller 270 such that when thebattery level falls below a predetermined value, a low battery signal isprovided from regulator 310 to microcontroller 270 to cause processor270 to go into the standby low power mode to be described.

Microcontroller 270 is powered (pin 14) from the V_(C) output ofregulator 310, and also has a master clear function (pin 4), such thateach time regulator 310 is enabled to produce V_(C), 1 μF/6 voltcapacitors 330 and 332 and 47 Kohm resistor 334 cooperate to provide atemporary master clear signal to microcontroller 270 to reinitiate theprocessing sequences thereof. Once the master clear function iscompleted, microcontroller 270 begins monitoring for a signal("near-boundary") on line 268 and a signal ("code-detect") on line 284as will now be described.

Normally, only transistor 276, flip-flop 292, and circuit 290 areenergized at all times (by V_(B)) with the output of flip-flop 292 at alogic high. Thus, the shutdown input of regulator 310 is pulled high andV_(C) is at a low level insufficient to power processor 270, forexample. Accordingly, processor 270 is powered down as are transistorswitches 264 and 280. Once every one-third second or so, V_(A) will gohigh for 30 milliseconds enabling the RF front-end amplifiers to detectRF energy on antennas 202, 204, 206. If insufficient signal is present,transistor 276 will remain biased off and V_(A) will be discontinued.The sequence of turning the amplifiers on and off will continue until asignal of sufficient strength is received to bias transistor 276 on. Asignal will then be coupled to the S input of flip-flop 292 as a resultof which several things will happen. Circuit 290 will turn the RF frontend full on and the shutdown input of regulator 310 will be pulled lowthrough diode 318 causing the supply V_(C) to be provided. Processor 270will then be powered up (and reset via the master clear) and transistorswitches 264 and 280 will be energized to produce boundary and detectsignals if appropriate.

If the received RF signal includes a valid code, as determined byprocessor 270 upon examination of the code-detect signal on line 284from amplifier 280, processor 270 which will then initiate an audibleannoyance signal to pet 18. To this end, a speaker enable signal isprovided on line 336 (from pin 13) to energize piezoelectric resonator340 in an attempt to cause pet 18 to move away from the source of theRF. Also, depending upon the state of switch 342 and whether thenear-boundary signal is also being provided, a shock will beadministered. Thus, if a valid detect signal is present and the RFsignal is sufficiently strong to cause amplifier 264 to output anear-boundary signal, then animal 18 is assumed to be too close toboundary 20 and a shock must be administered immediately. If, however,there is no boundary signal, then whether a shock is administeredimmediately or after a period of time if a valid detect signal continuesto be present after that period of time is dependent upon the setting ofcontrol switch 342.

To determine when and whether to administer a shock, processor 270responds to the state of selector switch 342 as determined upon eachpower-up of processor 270 as follows. Upon being powered-up (after themaster clear), microcontroller 270 outputs an interrogation signal onone of its data lines (pin 9) to the common terminal 344 of switch 342and monitors two other data lines (pins 8 and 11) for presence of thatsignal. Those lines are coupled to the high (H) and low (L) poles ofswitch 342 and are normally tied to a logic low through 1 megohmresistor 346 or the series combination of 1 megohm resistor 348 and LED350, respectively. The interrogation signal is normally onlyapproximately 200 milliseconds in length so that if switch 342 is in thelow or "L" position, there will be insufficient energy coupled through330 ohm resistor 348 and light emitting diode 350 to cause same to bevisually noticeable.

If switch 342 is in the high or "H" position, when interrogated, pin 8will receive a high signal and pin 11 will receive a low signal. Bycontrast, if switch 342 is in the Low or "L" position, when interrogatedpin 8 will receive a low signal and pin 11 will receive a high signal.If switch 342 is in the middle "delay" or "D" position, both pins 8 and11 will be low when they are examined upon interrogation of the signalfrom pin 9. The logic state received by microcontroller 270 at pins 8and 11 is used as follows.

If switch 342 is in the H position, a strong shock is to be producedimmediately upon validating the code-detect signal, just as if thenear-boundary signal had also been present. If switch 342 is in the Lposition, the shock will still be immediate but at a lower, moremoderate level. Finally, if switch 342 is in the D position, the shockwill be delayed for one (1) second and if, during that one (1) secondinterval, the code-detect signal remains valid, a strong intensity shockwill then be given. The delay in giving the shock allows pet 18 to moveaway from the boundary without receiving a shock. Of course, should anear-boundary signal appear during that one second interval, a shockwill then be immediately administered even though the delay period hasnot expired. If, however, during that one second interval, pet 18 movesaway from the boundary, the signals from the various amplifiers in theRF front end will decrease until they are too low to be detected, atwhich point, microcontroller 270 will determine that signals are nolonger present. No shock will thus be administered. Instead, a resetsignal (from pin 12) will be coupled to flip-flop 292 causing same toreset, whereafter circuit 290 will begin once again pulsing the RF frontend on and off. Additionally, regulator 310 will again be shut down andprocessor 270 powered down.

By virtue of switch 342, each receiver 200 may be set specific to eachanimal 18 wearing the receiver so that each animal in the area may begiven different delay periods and/or differing levels of shock asappropriate. The shock, once initiated, will continue until pet 18withdraws from the region of boundary 20 or a sufficient time periodpasses after which it is assumed that further shocks will be futile. Thelatter situation will be discussed in connection with the "keep alive"signal below. In the former situation, while microcontroller 270 ispowered up, lines 268 and 284 are monitored for the presence ofnear-boundary and code-detect signals. If pet 18 moves away from theboundary, the signals from the various amplifiers in the RF front endwill decrease until they are too low to be detected, at which point,microcontroller 270 will determine that signals are no longer present.At that point, processor 270 will terminate administration of shocks andwill output the reset signal to the R input of flip-flop 292 causingcircuit 290 to again go into the duty-cycle mode. As a consequence, theRF front end will again be powered on and off intermittently andprocessor 270 will be powered down until an RF signal of sufficientstrength is once again detected.

To produce a shock, a low frequency "zap" signal is produced fromprocessor 270 (e.g., from pin 10) and is coupled over line 360 to driveN-channel Mosfet transistor 362 (type MTD3055E1) of shock circuit 55 toturn same on and off. By turning transistor 362 on and off, energy isselectively coupled from battery 56 through 470 μF/16 volt capacitor 364to the primary coil 370 of step-up transformer 372 designed to accept a7.5 volt pulse and output at least a 3500 volt pulse (such as Part No.GTX 01-11539-2 available from Coil Tronics, Inc. in Pompano Beach,Fla.), the output coil 374 of which is coupled to probes 58 to initiatea high voltage shock to pet 18. The input or gate of transistor 362 isnormally tied to a logic low through 1 megohm resistor 376 to insurethat a shock is not generated unless a "zap" signal is actuallygenerated by microcontroller 270. In the H and D positions of switch342, the "zap" signal will be comprised of a continuous series of 500 μSpulses with 3 ms off-time between pulses to provide a strong shock. Inthe L position of switch 342, the "zap" signal will be a continuousseries of 350 μS pulses with 3 ms off-time between pulses to effectivelyprovide a lower level of shock to pet 18.

In training the pet, the H or L position would typically be useddepending upon the size of the pet. The D position may be selected laterwhen there is confidence that sound alone will likely cause pet 18 tomove away from boundary 20 without normally requiring a shock.

If a significant period of time passes, such as twenty seconds, and thesignal is still strong enough that a shock is still being given, thenlittle more should be attempted to deter animal 18. In this event,processor 270 goes into a low power monitor mode to conserve energy andstop shocking animal 18. In the monitor mode, the zap signal is notgiven. Instead, the reset signal is given so that the RF front end isagain duty-cycled on and off, but a low logic level keep alive signal isalso given. Normally, diode 320 is biased off by 100 Kohm pull-upresistor 338. The keep alive signal is coupled through diode 320 tocause regulator 310 to continue to output V_(C) and thus maintainprocessor 270 powered up so that its memory contents are not lost. Butin the monitor mode, processor 270 merely monitors for the code-detectsignal to determine if it terminates for a period of time, e.g., 4seconds. Unless the code-detect signal is absent for the full timerequired, processor 270 remains in the low-power state with the keepalive signal maintained (and no zap signal generated). If thecode-detect signal is absent for a full 4 seconds, the keep alive signalis terminated allowing regulator 310 to shut down and power downprocessor 270. Normal operation as previously described will then ensue.But by being in the low-power monitor mode, continued detection ofnear-boundary and code-detect signals will not cause a zap signal thuspreventing harm to pet 18 and conserving battery power. A low-powerstandby mode may also be entered if a low battery signal is receivedfrom regulator 310 (such as at pin 2 of processor 270). In that case, anintermittent signal (e.g., a 50 ms pulse) will be provided fromprocessor 270 (on pin 9) sufficient to flash LED 350 on and off. LED 350is mounted to be visible from the exterior of housing 27 so that thepet's owner will have a visible warning that the battery needs to bechanged. Additionally, and unlike the monitor mode of low poweroperation when a shock has been administered for a long period of time,the low-battery standby mode operates to provide normal functionality tothe receiver, but in a power conservation mode. To this end, theprocessor goes into a "sleep" mode during which its power consumption isvery low. An internal watchdog timer (not shown) begins to time out and,when it does, processor 270 "wakes up." Upon waking up, processor 270examines the code-detect and near-boundary signal lines for validsignals and also outputs a signal to flash the LED on and off. If novalid signal is present, processor 270 again goes into the sleep mode toawait the next time out of the watchdog timer. But, if a validcode-detect signal is present, then operation will be as previouslydescribed for full power operation with respect to the administration ofannoyance signals and the like.

A second embodiment of a microprocessor-based receiver 200A isillustrated in FIG. 6. Operation of receiver 200A is similar to receiver200, except that the three orthogonally positioned antennas 202, 204,and 206 are, once again, sampled and control of the power duty-cyclingis simplified. To this end, regulator 310 and power cycle or timercircuit 400 cooperate to duty cycle the circuitry of receiver 200A onand off. More specifically, the shutdown input (pin 5) of regulator 310is no longer tied high, but is instead controlled through power cyclecircuit 400 which is responsive to the shutdown signal from processor270 to turn off for about 1/3 second and then turn back on. Whileregulator 310 is off, the RF front end 402 and microprocessor 270 arepowered down to conserve battery power. After the 1/3 second, circuit400 times out allowing regulator 310 to turn back on and supply V_(C) topower RF front end 402 and processor 270.

When processor 270 first powers up, it goes through a master clear anddetermines the state of switch 342, all as previously described (withmodifications to the RC circuit coupled to pins 4 and 14 as shown inFIG. 6 including the addition of 56 ohm resistor 335). Processor 270then begins to examine the antennas. To this end, processor 270 outputsa signal on one of its data lines (e.g., pin 6) to turn on analog switch404 for about 11-12 ms. When switch 404 is on, RF energy on antenna 202may be detected as will be described. If no signal is detected, analogswitch 404 is turned off and processor 270 will output a second 11-12 mssignal on another data line (e.g., pin 7) to turn on second analogswitch 406 coupled to second antenna 204 to thereby monitor for energytherefrom. Here again, if no signal is detected, then switch 406 isturned off and a third 11-12 ms signal from another data line (e.g., pin8) is output from processor 270 to turn on third analog switch 408 todetect RF energy from third antenna 206. Each of switches 404, 406 and408 are normally held in the off state by a respective 1 megohm ("Mohm")resistor 410 coupled between the gate thereof and ground. If no signalis detected from any of the three antennas, the shutdown signal isissued to power cycle circuit 400 to turn off regulator 310 for 1/3second and power down receiver 200A.

Whenever one of antennas 202, 204 and 206 is selected (by turning on itsassociated switch 404, 406, and 408), energy therefrom resonates withparallel 0.022 μF capacitor 412. If RF energy is present on the selectedantenna to resonate with capacitor 412, the signal is coupled toamplifier 414 of RF front end 402. More specifically, the signal iscoupled to the base of grounded emitter NPN transistor 420 via 4700 pFcapacitor 422. The collector of transistor 420 is coupled to V_(C) via100 Kohm resistor 424 and is also coupled for negative feedback to itsbase via 2.2 Mohm resistor 426. The base thereof is further coupled toground via 820 Kohm resistor 428. The amplified signal from transistor420 is coupled via 1000 pF capacitor 430 to the base of second groundedemitter NPN transistor 432 which is similarly biased by a second set ofresistors 424, 426 and 428. The output of transistor 432 is coupled via470 pF capacitor 434 to the base of third grounded emitter NPNtransistor 436, the collector of which is coupled via 330 Kohm resistor438 to V_(C) and employs a 3.3 Mohm negative feedback resistor 440.

The output of amplifier 414 is coupled to detector 441 comprised of theseries circuit of diode 442 and 68 Kohm resistor 444 coupled to the baseof NPN emitter follower transistor 446. The collector of transistor 446is tied to V_(C) and the emitter thereof is coupled to ground via 430Kohm resistor 447 and 560 Kohm resistor 448 to provide at the emitter asignal corresponding to the modulation on any received RF signal. Thedemodulated signal is coupled via 100 Kohm resistor 449 from the emitterof transistor 446 to the base of grounded emitter NPN transistor switch450 to provide a micro-processor compatible digital signal correspondingto the modulation in the received RF signal. The collector of switch 450is coupled to V_(C) via 1.0 Mohm resistor 452 and to pin 1 of processor270 to provide the code-detect signal utilized by processor 270 todetermine whether to administer an annoyance signal. An attenuateddemodulated signal is present at the junction of resistors 447 and 448.If the attenuated signal is of sufficient strength, then a near-boundarysignal is to be given to cause immediate administration of a shock(provided a valid code-detect signal is also present). To this end, theattenuated signal is coupled via 1.0 Kohm resistor 454 to the base ofgrounded emitter NPN transistor switch 456 to similarly provide adigital signal for utilization by processor 270. The collector oftransistor 456 is coupled to V_(C) through 2.2 Mohm resistor 458 and topin 18 of processor 270 to provide the digital near-boundary signal.

The output from transistor 450 is coupled to processor 270 as thecode-detect signal previously described in connection with receiver 200for evaluation. If the code-detect signal is the proper 90 Hz codedsignal, for example, then an annoyance signal, such as a sound and/orshock is administered. An audible annoyance signal will be generated inany event as previously described. And a shock annoyance signal is alsogiven in accordance with either the state of switch 342 or presence ofthe near-boundary signal as also previously described.

As an alternative to the use of switch 456, a different test forattenuated RF signals could be undertaken. In this case, if switch 342indicates a possible delay may be incurred (i.e., switch 342 is in the Dposition), upon detecting a valid code-detect signal, processor 270could output a signal (such as from pin 18) to an attenuator circuit 460(shown in phantom in FIG. 6) which reduces the signal level receivedinto amplifier 414. Transistor 462 of circuit 460 is normally biased offby pull-down resistor 464 but in response to the signal from processor270 turns on to sink current from the input of amplifier 414 throughresistor 466 and transistor 462 to thus attenuate the signal toamplifier 414. The code-detect signal is then evaluated based upon theattenuated signal. If the code-detect signal is still valid, even thoughthe RF signal has been attenuated, then it may be assumed that pet 18 issufficiently close to the boundary to warrant a shock. Accordingly, azap signal will be generated to shock the animal just as if thenear-boundary signal had been provided by switch 456. However, if thecode-detect signal is not able to be validated when the RF signal isattenuated, then it is assumed that the pet is near enough to theboundary to warrant an audible annoyance signal, but no so close as tobe in immediate danger of crossing through the boundary. Thus, a shockis not immediately necessary and none is given unless the otherrequirements are met as described in connection with receiver 200 or theattenuated signal raises to a level sufficient to provide a validatedcode-detect signal.

In the event a valid code-detect signal is present, the switch 404, 406,408 which was turned on is held on for continued processing of signalsfrom the associated antenna 202, 204 or 206.

Power circuit 400 is provided for purposes of duty-cycling RF front end402 and processor 270. Power circuit 400 includes Mosfet switch 490 theinput or gate of which is normally tied to V_(C) via 1 Mohm pull upresistor 492 to V_(C) and also coupled to pin 12 of processor 270 toreceive a digital low "shutdown" signal when regulator 310 is toshutdown. The source of switch 490 is also coupled to V_(C) with thedrain coupled to the shutdown input of regulator 310 and to RC timercircuit comprised of 0.1 μF capacitor 494 in parallel with 3.3 Mohmresistor 496 coupled to ground. When regulator 310 is on, and processor270 is not outputting the shutdown signal, switch 490 is turned off suchthat the shutdown input of regulator 310 is pulled via the RC circuit toa logic low thus maintaining regulator 310 powered up to output V_(C).Upon receipt of a shutdown signal from processor 270 to activate timer400, switch 490 closes allowing capacitor 494 to charge up at a ratedetermined by the RC time constant until the shutdown input of regulator310 sees a logic high level and thus shuts off power to RF front end 402and processor 270. As a result, the shutdown signal will terminate andswitch 490 will not be powered. Regulator 310 will be held off for thetime it takes capacitor 494 to discharge to a logic low level (about 1/3second) to again cause regulator 310 to power up and output V_(C) toturn RF front end 402 and processor 270 back on as previously described.

While particular examples of operation of processor 270 are describedherein, other techniques could be employed. A listing of the object codefor programming processor 270 to operate as described in connection withFIG. 6 is set forth in Appendix A included herewith and incorporatedherein by reference.

The resistor components that are common to receivers 200 and 200A are ofslightly different values as set forth in the following table:

    ______________________________________                                        Resistor Component                                                                           Value in Receiver 200A                                         ______________________________________                                        Resistor 312   8.2 Mohm                                                       Resistor 314   2.2 Mohm                                                       Resistor 324   1.0 Mohm                                                       Resistor 326   1.5 Mohm                                                       Resistor 348   130 ohm                                                        ______________________________________                                    

A 0.1 μF decoupling capacitor 498 is provided between V_(C) and ground.Also, the base of each transistor 450, 456 may be coupled to ground witha respective 0.01 μF capacitor (both not shown) to reduce noise and highfrequency signals that might hamper operation of processor 270.

The component values selected herein may vary depending upon the sizeand type of housing 27 as well as the physical layout of the componentswithin housing 27. Thus, as certain components are located close toprobes 58, the high voltage signals therefrom may necessitatemodification to the circuity or component values above described. Forexample, and with reference to FIGS. 6A and 6B, drivers for speaker 340and low-battery LED 350 may be useful. To this end, resistor 348 may bedispensed with and pin 11 of processor 270 and the L-contact of switch342 coupled to ground by a 1 Mohm resistor 600 and to the gate oftransistor 602. LED 350 is coupled in series with 150 Ohm resistor 604between V_(C) and the source of transistor 602, the drain of which isgrounded. Similarly, for speaker 340, pin 13 of processor 270 is coupledto ground through a 1 megohm resistor 606 and to the gate of transistor608. Speaker 340 is coupled between V_(C) and the source of transistor608, the drain of which is also grounded. Power circuit 400 is modifiedas shown in FIG. 6C. In this case, the shut-down signal from pin 12 ofprocessor 270 is coupled directly to the RC circuit of capacitor 494 and496 and to the gate of transistor 610, the drain of which is groundedand the source of which is coupled to the battery voltage (V_(B)) via 1megohm resistor 612. The source of transistor 610 is further coupled toground via 1 μF capacitor 614 and to the gate of second transistor 616,the drain of which is grounded and the source of which is coupled toV_(B) through 2.2 megohm resistor 618 and to pin 5 of regulator 310.Processor 270 is programmed to output a digital high "shut-down" signalwhen regulator 310 is to turn off instead of a digital low signal aspreviously described for power circuit 400 of FIG. 6.

As shown in FIG. 7, receiver 200A may be modified to be responsive to amotion sensor-based battery power conservation technique. To this end,processor 270 is normally powered on at all times and controls the stateof MOSFET switch 500 to selectively power-up RF front end 402. Processor270 monitors for signals from one or more fluid-filled andperpendicularly oriented vibration sensors 502 which indicate that pet18 is moving. If there is movement as indicated by a signal from sensors502, processor 270 will output an "on" signal over line 504 to closeswitch 500 and turn RF front end 402 on. Signals from RF front end 402are then examined, or interrogated, for a period of time, as previouslydescribed for up to 4 seconds, and if no proper code-detect signals, forexample, are detected during that time, then processor 270 willterminate the "on" signal causing switch 500 to open and turn RF frontend 402 off. If, however, such signals are detected, processor 270 willinitiate the audible and shock annoyance signals as appropriate. Theabove sequence is activated every time there is a signal from sensors502.

Processor 270 could alternatively be programmed to automatically turn RFfront end 402 on at selected intervals which vary in accordance with theamount of movement of pet 18. Thus, for example, if pet 18 is veryactive, signals will be provided at a great rate from sensors 502. Inthat case, RF front end 402 may be turned full on until the rate ofsignals from sensors 502 begins to abate. If the activity level is onlymoderate, RF front end will be turned on every 0.5 seconds whereas ifthere is only slight motion, RF front end will be turned on only everysecond or so. Moreover, if the activity is so slight that there has beenno motion for at least one minute, RF front end will be interrogatedonly every 15 seconds. Of course, whenever RF front end 402 is on,signals therefrom will be interrogated and, if appropriate, annoyancesignals will be administered to cause pet 18 to move away from wire 20.If the pet remains idle for up to thirty minutes, no furtherinterrogation of RF front end will occur until there is further movementby pet 18. Since many pets spend a great deal of time resting orsleeping, the motion sensors may reduce the amount of time the RF frontend is on to about 10% of the time.

It will be appreciated that shocks are communicated to the neck of pet18 by shock transfer probes 58 extending from housing 27 slung on theneck of pet 18. Housing 27 may be 11/4" H by 15/8" W by 2", and probes58 may be extended metal lugs extending from housing 27 as isconventional. As shown in FIGS. 8 and 9, probes 58 may alternatively bemade of softer material so as to reduce abrasion of the pet's neck. Tothis end, two metal posts 520 (only one shown) are provided extendingfrom housing 27. Posts 520 have a central threaded bore 522 to bethreadably received on threaded lug 524 mounted to housing 27 inelectrical communication with shock circuit 55 or shock transformer 372.Posts 520 each have a base portion 526 and a support portion 528, thelatter having a "Christmas tree" like exterior with vertical,anti-rotation notches 530 extending along the periphery thereof. Aconductive plastic tip 532 has a central aperture 534 sized to be snuglyreceived over the support portion 528 to thus secure tip 532 to support520. Tips 532 may be injection molded material having a hardness of 70durometer, such as Part No. 2899X53675F from RTP Co. in Winona, Minn.Tips 532 are formed to have a shaped end 536 which is about 0.14 or 0.15inches thick (measured from the central aperture 534 to the veryterminus 540 of tip shaped end 536). The sidewall 542 of shaped end 536is slanted at an angle of about 45° relative the longitudinal axis oftip 532.

Tips 532 provide a softer and more compliant surface against the neck ofpet 18 than conventional metal lugs employed to communicate the shock tothe pet. The tips 532 thus serve to protect pet 18 and make use of thesystems of the present invention more readily accepted by owners (notshown). To accommodate pets of various sizes, posts 520 may be ofdifferent lengths. To this end, the support 528 is about 0.22 inches inlength and base 526 is of such size that posts 520 extend from housing27 a total of about 0.34 to 0.60 inches. The desired spacing correlatesto the size of pet 18 on which receiver 26 will be used.

In use, area 16 is defined by the placement of wire 20 in the area tocontain pet 18, and wire 20 connected to transmitter 22 (or 22A). Thereceiver, such as receiver 26, 26A, 200 or 200A, is mounted to a collar28 and placed securely around the neck of pet 18 with probes 58 facingagainst the neck. As pet 18 moves about the bounded area, if the petshould move towards boundary 20, an RF signal will be detected andevaluated for the proper "code". If detection is confirmed, an audibleannoyance signal and a shock annoyance signal will be given (or a shockadministered after a delay depending upon the setting of switch 74 or342) to cause pet 18 to back away from the boundary line.

By virtue of the foregoing, there is thus provided an electronic animalconfinement system, and receiver and transmitter components therefor,which overcome various drawbacks associated with prior art confinementsystems.

While the present invention has been illustrated by description ofseveral embodiments and while the illustrative embodiments have beendescribed in considerable detail, it is not the intention of applicantsto restrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. For example, multiple switches to provideindependently selectable shock levels and delays may be provided.Similarly, other techniques of duty cycling the RF front end and/orprocessor may be provided. Also, where motion sensors are used, thefrequency of interrogation may also be made to depend not only on motionactivity, but also on the setting of the delay or shock level switch asdesired. Still further, although described in connection with a pet,such as a dog, it will be appreciated that the present invention isequally applicable with any domesticatable animal. The invention in itsbroader aspects is therefore not limited to the specific details,representative apparatus and methods, and illustrative examples shownand described. For example, although three orthogonally positioned ororiented antennas are desirable, many of the features are applicable tosystems wherein the receiver has one or two antennas. Accordingly,departures may be made from such details without departing from thespirit or scope of applicants' general inventive concept.

APPENDIX A Electronic Animal Confinement System

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We claim:
 1. A receiver adapted to be supported on an animal to confinethe animal behind a boundary defined by a boundary signal, the receivercomprising:a housing; at least one antenna supported within the housing;a source of annoyance signals; receiver circuitry coupled to the sourceof annoyance signals and the antenna and adapted to enable the annoyancesignals in response to receipt of a boundary signal on the antenna;battery means for powering at least the receiver circuitry; a lowvoltage indicator operable in response to low voltage of the batterymeans to provide an alert when the battery is nearing the end of itsuseful life; and duty cycle circuitry coupled to the receiver circuitryand selectively coupling power between the battery means and thereceiver circuitry to turn same on and off responsive to the low voltageindicator whereby to conserve power.
 2. The receiver of claim 1 furthercomprising circuit means for monitoring voltage of the battery means,the circuit means having an output providing the low voltage indicatorin response to said low voltage of the battery means.
 3. The receiver ofclaim 2 further comprising indicator means coupled to the low voltageindicator for providing said alert.
 4. The receiver of claim 3 whereinthe indicator means includes a light emitting diode.
 5. The receiver ofclaim 1 further comprising indicia associated with the housing andresponsive to the low voltage indicator to provide said alert.
 6. Thereceiver of claim 1 wherein the low voltage indicator includes indicatormeans for providing said alert.
 7. The receiver of claim 6 wherein theindicator means includes a light emitting diode.
 8. The receiver ofclaim 6 further comprising circuit means for monitoring voltage of thebattery means, the circuit means having an output coupled to the lowvoltage indicator.
 9. The receiver of claim 1 further comprising controlcircuitry coupled to the duty cycle circuitry and responsive to receiptby the antenna of a boundary signal to interrupt action of the dutycycle circuitry whereby to maintain the receiver circuitry turned on.10. The receiver of claim 1 wherein the receiver includes threeorthogonally positioned antennas and the receiver circuitry is coupledto the antennas and responds to receipt of a boundary signal on at leastone of the antennas.
 11. The receiver of claim 10 further comprisingswitch circuitry coupled to the antennas and selectively coupling, oneat a time, one of the three antennas to the receiver circuitry.
 12. Thereceiver of claim 1 further including at least one electricallyconductive probe coupled to the source of annoyance signals whereby tocommunicate a shock to said animal.
 13. The receiver of claim 12 whereinthe probe includes an electrically conductive, compliant tip.
 14. Amethod of confining an animal behind a boundary defined by a boundarysignal, the method comprising:generating a boundary signal; emitting theboundary signal from an emitter to define the boundary; monitoring inthe vicinity of the animal for the boundary signal, the monitoring beingaccomplished with electronic circuitry powered by a battery; dutycycling the electronic circuitry on and off to conserve battery power;generating an annoyance signal to the animal if the boundary signal isreceived; monitoring voltage of the battery; and providing an alert whenthe battery is nearing the end of its useful life.
 15. The method ofclaim 14 wherein said providing an alert step includes selectivelyenergizing a visible indicator.
 16. The method of claim 14 furthercomprising communicating a shock to the animal by coupling the annoyancesignal to an electrically conductive, compliant tip of a probe.